Safety control for load line

ABSTRACT

A safety control mechanism for a load line forming part of an extensible boom crane which has a plurality of sections moved relative to each other by power means. The cable supports a load supporting member on one of the crane sections and is reeled or unreeled from a driven drum supported adjacent another of the sections. The safety control means incorporates mechanism which will render the power means inoperative when the tension on the cable reaches a certain level. The safety control means consists of a bracket pivotally supporting the drum and pivoted about an axis. The bracket is normally biased to a first position, with the biasing means accommodating movement from the first position after the tensile load exceeds a lower level to actuate control means, forming part of the power means, to render the power means inoperative when the tensile load on the cable exceeds a desired maximum level.

United States Patent Lamer et al.

[54] SAFETY CONTROL FOR LOAD LINE [72] Inventors: Gerald P. Lamer,Rothschild; Lembit [21] Appl.No.: 42,837

LORD LINE PULL 129,317 6/1960 U.S.S.R. ..2l2/39 B Primary Examiner-EvonC. Blunk Assistant E.t'aminer-W. Scott Carson Attorney-Dressler,Goldsmith, Clement 84 Gordon [57] ABSTRACT A safety control mechanismfor a load line forming part of an extensible boom crane which has aplurality of sections moved relative to each other by power means. Thecable supports a load supporting member on one of the crane sections andis reeled or unreeled from a driven drum supported adjacent another ofthe sections. The safety control means incorporates mechanism which willrender the power means inoperative when the tension on the cable reachesa certain level. The safety control means consists ofa bracket pivotallysupporting the drum and pivoted about an axis. The bracket is normallybiased to a first position, with the biasing means accommodatingmovement from the first position after the tensile load exceeds a lowerlevel to actuate control means, forming part of the power means, torender the power means inoperative when the tensile load on the cableexceeds a desired maximum level.

2 Claims, 3 Drawing Figures BACKGROUND OF THE INVENTION The presentinvention relates generally to mobile hoisting equipment and, moreparticularly, to overload safety control mechanism for extensible cranesections and the like.

Present day heavy duty cranes generally consist of a plurality of cranesections defining an extensible boom which has a load supporting blockmovably supported on the outer free end of the boom. The load supportingblock is normally raised and lowered relative to the free end of theboom by a winch drum supported adjacent the innermost boom section andentrained over a pulley rotatable on the outer end of the boom. Thecrane assembly is generally supported on a self-propelled vehicle by arotating base section for the crane.

Various proposals have been made for controlling the maximum load whichmay be supported on the cantilevered boom as well as cooperating controlmechanisms to prevent the extension of the boom sections and the angularposition of the boom beyond predetermined limits while a load issupported on the block, which would tend to tip the vehicle. While thesesafety controls have been effectively incorporated into mobile cranes toprevent damage to the vehicle or the crane, one area which has notreceived any attention is prevention of the cable from being fracturedwhile the boom is being extended.

The extension and retraction of the boom sections is presently,generally, being accomplished through the use of fluid rams withhydraulic fluid delivered from a source to opposite ends of the rams.Generally, such extension and retraction occurs when no load is beingsupported by the load supporting member. One of the problems which hasarisen in connection with the use of hydraulic motors for extension andretraction of the boom sections is that it becomes necessary for theoperator to at all times be cognizant of the position of the loadsupporting member relative to the crane to prevent snapping of thecable. Thus, it is necessary for the operator to devote his entireattention to the extension of the boom sections when such need arises.

SUMMARY OF THE INVENTION The present invention contemplates a safetycontrol means for a crane having a plurality of boom sections and powermeans to extend and retract the sections relative to each other and, inwhich a load supporting member is movable relative to the outer end ofthe outer boom section through a cable having one end connected to adriven reel supported adjacent the inner end of the boom. The safetycontrol means corporates with the driven reel and the power means forthe crane section to render the power means inoperative when the tensionon the cable reaches a predetermined level.

More specifically, the present invention contemplates a drive means forthe cable in the form of a powered winch or reel which is rotated inopposite directions to raise and lower the load supporting member orblock with the safety control means including mechanism for movablysupporting the reel and biasing means normally urging the mechanism to afirst position. The mechanism includes a bracket supporting the cabledrum for rotation about a pivoted axis with the bracket in turn beingpivoted about an axis on a support member and urged to a first positionby a spring. Thus, as the tension on the cable increases, the bracket ispivoted from the first position and upon reaching a second position,renders the power means inoperative. The means for rendering the powermeans inoperative includes a normally open valve located in a conduitleading from a fluid pressured source to fluid rams with an actuatingmember carried by the bracket to close the valve when the bracket ismoved to the second position.

With the present arrangement, the spring biased bracket acts as sensingmeans for determining the load or tension on the cable and the valve isoperated by the sensing means to render the power means inoperative whenthe load or tension reaches a predetermined level.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF DRAWINGS FIG. 1 is a sideelevation view of a vehicle mounted crane, having the inventionincorporated therein;

FIG. 2 is a fragmentary plan view taken generally along line 2-2 ofFlG.1; and

FIG. 3 is a vertical sectional view taken along line 3-3 of FIG. 2.

DETAILED DESCRIPTION While this invention is susceptible of embodimentin many different forms, there is shown in the drawings and will hereinbe described in detail one specific embodiment, with the understandingthat the present disclosure is to be considered as an exemplification ofthe principles of the invention and is not intended to limit theinvention to the embodiment illustrated.

The safety control means of the present invention is illustrated asembodied in a self-propelled crane having a frame or chassis 10supported on wheels 12 (FIG. 1). A suitable power plant 14 is carried bythe frame and may be connected to the wheels to move the frame. Thevehicle frame 10 supports a crane consisting of a base section 16rotatable about the vertical axis on the frame 10. An extensible boom 20is pivoted adjacent the upper end of the base section 16 to swing abouta horizontal axis through extension and retraction of a fluid ram 22having opposite ends respectively connected to the base section 16 andthe crane 20.

The extensible boom 20 consists of a plurality of boom sections 24, 26,and 28 with the section 26 being telescoped within the section 24 andthe section 28 being telescoped within section 26. The extension andretraction of the respective boom sections relative to each other isaccomplished through first and second rams 30 and 32 with fluid ram 30being pivotally connected at one end to the boom section 24 and at itsopposite end to boom section 28. Likewise, fluid ram 32 is pivotallyconnected at one end to the intermediate boom section 26 and at theopposite end to the outer boom section 28. Pressured fluid is suppliedfrom a source (not shown) through conduits, one of which is shown at 34,to the respective fluid rams 30 and 32 to cause extension and retractionof the boom sections relative to each other.

The crane further includes a block or load supporting means 40 supportedon the outer free end of the outer boom section 28 through a cable 42.The cable 42 has one end connected at 44 to the outer crane section 28and extends around a pulley within the block 40 and across at least oneguide pulley 46 on the outer crane section 28 and a second guide pulley47 rotated on the inner end of boom section 24. The opposite end of thecable is connected to a driven reel or winching drum 48 which is capableof being rotated in opposite directions through suitable drive means 50.Thus, rotation of the reel 48 in a counterclockwise direction as viewedin FIG. 1 will allow the block 40 to be lowered relative to the outerend of the boom, while clockwise rotation will raise the block or loadsupporting member relative to the crane boom 20.

An inspection of FIG. 1 reveals that the reel or drum having one end ofthe cable afiixed thereto is essentially fixed relative to the innerboom section 24 while the opposite end of the cable is fixed at 44 tothe outer boom section 28. With the load supporting member 40 located inthe position shown in FIG. 1, extension of the boom sections relative toeach other cannot be accomplished without first unreeling a portion ofthe cable sufficient to lower the block 40 an amount that willaccommodate extension of the boom sections without having the blockengage the boom section 28. Thus, if the operator inadvertently fails tounreel the cable 42 and begins extension of the boom sections, thepressure of the fluid received into the rams 30 and 32 will producesufi'icient forces to cause the cable to snap. Such an arrangementproduces a safety hazard, since the cable may cause injury to theoperator as well as damage to the vehicle. Furthermore, if the cable isfractured, it necessitates a considerable shut down period to remove andreplace the entire cable.

However, according the present invention, the above problem isalleviated by a simple and inexpensive mechanism which willautomatically render the fluid rams or power means inoperative when thetension or load on the cable reaches a predetermined level. The safetycontrol means of the present invention consists of a minimum number ofparts which are extremely inexpensive and which cooperate in aneffective manner to achieve the intended results. More specifically, theentire mechanism consists of a valve, a bracket and at least one spring.The three elements are arranged in such a manner that the flow ofpressured fluid to the rams or power means 30 and 32 is blocked wheneverthe tension on the cable reaches a desired maximum level. The threeelements cooperate to define sensing means for determining the load onthe cable and means responsive to said sensing means for rendering thefluid rams inoperative when the load reaches a predetermined maximumlevel. Referring to the drawings, the sensing means consists of asubstantially U-shaped bracket 60 having leg portions 62 pivotallysupported on upwardly extending standards 64 through pivot pins 66. Thestandards are part of a base 67 extending from the base section 16. Thebracket 60 has an additional leg 68 extending upwardly from the webportion at a location betwen the two legs 62 with the drive means ormotor 50 secured to the leg 68. The drive means has a driven shaft 70extending through the leg 68 and connected to the drum 48, which isrotatably supported between one leg 62 and the opposite intermediate leg68.

The bracket cooperates with biasing means and a stop to define a firstposition for the sensing means. For this purpose, an adjustable stop 72is fixedly secured to the base 67 defining the support means for theuprights 64. The adjustable stop is located in alignment with the webportion of the bracket 60 and the bracket 60 is biased to a firstposition, where the bracket engages the stop, by biasing means 74 in theform of a pair ofleafsprings.

Thus, the sensing means including the U-shaped bracket 60 and thesprings 74, as well as the stop 72, cooperate to define a first positionfor the bracket when the tension on the cable is below a predeterminedlevel. However, once the tension on the cable exceeds this power level,the tangential force developed by the load along the periphery of thedrum 48 will cause the bracket to pivot from the first position as afunction of the tension or load on the cable. When the tension or loadon the cable reaches a desired maximum level, a stop mechanism or means,to be described later, cooperating with the power means, is actuated torender the power means inoperative.

in the illustrated embodiment, the stop mechanism or means includes anormally open valve 80 incorporated in the conduits connecting the powersource to the fluid rams or motor means 30 and 32. An actuating element82 extends from the valve means 80 and the bracket 60 has an arm 84extending to a position in alignment with the actuating member 82 sothat rotational movement or pivoting of the bracket will cause the freeend of the arm to move the actuating member 82 to a second position andclose the valve. Closure of the valve, will block the flow of fluidthrough conduit means 34 and thereby render the fluid rams inoperative.

lt will be appreciated that the present invention is a simple,inexpensive and effective way of preventing the snapping of the cablebecause of the inattention of the operator. This arrangement allows theoperatormore freedom in performing other functions while he is extendingthe boom sections relative to each other. In addition, the mechanismincludes a minimum number of parts, which can readily be incorporatedinto existing cranes so that any crane of this general character canreadily be converted to include the safety control means.

While the driven reel and the valve have been shown as being supportedon the rotatable base, it is readily apparent that these elements couldbe mounted directly on the inner boom section 24. It should also benoted that, it may be desirable for the predetermined maximum load onthe cable, which will render the power means inoperative, to be greaterthan the desired maximum load on the block so that the boom sectronsmay, if desired, be extended and retracted while a load is beingsupported by the block and the cable.

What is claimed is:

1. An implement comprising: a frame; a boom supported on said frame andincluding a plurality of boom sections; means for adjusting the angularorientation of the boom relative to a horizontal axis on the frame;power means for extending said boom sections relative to each other;load support means on one of said sections; a cable supporting said loadsupport means; a driven reel connected to said cable and operable tomove said load support means relative to said one of said sections;means mounting said reel at a fixed location relative to said boomincluding a bracket supporting said reel for rotation about an axis;sensing means for determining the load on said cable and includingmounting means pivotally supporting said bracket for movement about saidaxis, spring means urging said bracket to a first position andpennitting said bracket to pivot about said axis when the load on saidcable reaches a predetermined level; and means responsive to pivotalmovement of said bracket for rendering said power means inoperative whenthe load on said cable reaches said predetermined level.

2. An implement as defined in claim 1, in which said power meansincludes a fluid ram, a fluid source and conduit means connecting saidsource to said ram and in which said means responsive to pivotalmovement of said bracket includes valve means in said conduit means andmounted at a fixed location relative to said bracket, and an actuatorcarried by said bracket and adapted to operate said valve means uponpivotal movement of said bracket.

1. An implement comprising: a frame; a boom supported on said frame and including a plurality of boom sections; means for adjusting the angular orientation of the boom relative to a horizontal axis on the frame; power means for extending said boom sections relative to each other; load support means on one of said sections; a cable supporting said load support means; a driven reel connected to said cable and operable to move said load support means relative to said one of said sections; means mounting said reel at a fixed location relative to said boom including a bracket supporting said reel for rotation about an axis; sensing means for determining the load on said cable and including mounting means pivotally supporting said bracket for movement about said axis, spring means urging said bracket to a first position and permitting said bracket to pivot about said axis when the load on said cable reaches a predetermined level; and means responsive to pivotal movement of said bracket for rendering said power means inoperative when the load on said cable reaches said predetermined level.
 2. An implement as defined in claim 1, in which said power means includes a fluid ram, a fluid source and conduit means connecting said source to said ram and in which said means responsive to pivotal movement of said bracket includes valve means in said conduit means and mounted at a fixed location relative to said bracket, and an actuator carried by said bracket and adapted to operate said valve means upon pivotal movement of said bracket. 